Printer/plotter sheet transport with web cutting means

ABSTRACT

Paper from a continuous roll is fed into a loop by first rollers at a given speed and out of the loop by second rollers at a lower speed, the first rollers are stopped to permit tear-free cutting of the paper into sheets after the first rollers have rotated sufficient times to pass a length of paper equivalent to the desired length of sheet indicated by controllable settings. Restarting of the first rollers is timed to permit successive sheets to pass to the second rollers with a minimum, selectible intersheet spacing. Individual jam detection, for several sheets concurrently within the transport, is effected by utilizing a shift register to shift bits inserted therein in timed relation with the passage of related sheets, successive bits concurrently in the register corresponding to related successive sheets concurrently within the transport. Sheets are logged in and logged out to cause the transport to run until all sheets are clear. The above features are provided in a variable speed paper transport.

[ PRINTER/PLOTTER SHEET TRANSPORT WITH WEB CUTTING MEANS [75] Inventors: David L. Sharp, New Britain;

Douglas P. Modeen, lSouthington, both of Conn.

[73] Assignee: United Aircraft Corporation, East Hartford, Conn.

[22] Filed: Aug. 26, 1970 [21] Appl. No.: 67,168

[ July 3, 1973 3,654,830 4/1972 I Werner, Jr 83/208 3,670,614 6/1972 Streckert 83/208 Primary Examiner-Samuel S. Matthews Assistant Examiner-Richard M. Sheer AtrorneyMelvin Pearson Williams [5 7] ABSTRACT Paper from a continuous roll is fed into a loop by first rollers at a given speed and out of the loop by second rollers at a lower speed, the first rollers are stopped to permit tear-free cutting of the paper into sheets after Cl 9, 355/3, 355/13, the first rollers have rotated sufficient times to pass a 83/208, 83/209, 83/210, 83/369 length of paper equivalent to the desired length of sheet [51 1 Int. Cl. G03b 29/00 indicated by controllable settings. Restarting of the first [58] Field of Search 355/11, l3, 14, 28, rollers is timed to permit successive sheets to pass to 355/29, 3; 83/208, 209, 210, 369 the second rollers with a minimum, selectible intersheet spacing. Individual jam detection, for several [56] References Cited sheets concurrently within the transport, is effected by UNITED STATES PATENTS utilizing a shift register to shift bits inserted therein in 3,639,053 2/1972 Spear, Jr 355 13 time? reiatim with the f of ,related Sheets 9 3,513,741 5/1970 Shauenberg 83/210 X cessive bits concurrently tn the register corresponding 3,538,726 11/1970 Cook 83/369 x i to related successive sheets concurrently within the 3,645,157 2/1972 DiGiulio et a]. 355/13 X transport. Sheets are logged in and logged out to cause 3,406,601 10/ 1968 Clifford 83/369 X the transport to run until all sheets are clear. The above 3,418,047 12/1968 Lee et al 355/13 X features are provided in a variable speed paper trans- 3,504,586 4/1970 Acquaviva, Jr..... 83/208 X pom 3,524,371 8/1970 Kroger 83/369 3,639,055 2/1972 Schleifenbaum 355/29 3 Claims, 7 Drawing Figures P/P/NTE/P (ML- TRANS PM (30) EQEQAI FR'NT iii. P PER A 71/, TRANSPORT MOTOR CTRL I L PAPER F EEDE R r MOTOR 2 5 1 ,W r i CTRL j// I, O DEVELOPER 6 4 B E R W Q1 .2 7 724 V STACKER (PAPER SOP).

PAPER TRANSPORT l PAPER FEEDER PATENTED JUL 3 ms MEI 3 (if 6 FIG. 3

fffl 2 2 My Y {4% PAPR 2 SYNC S N [PAP SENS 2 C Q (fly W r [145 SYN CLK Q ROLR SYNC JROLLER C C 1M SYN CLK ROLR 2 SYNC 3 Q [ROLLER 2 9%; C NC 3% 7'47} 5 FE Z74 SYN CLK Q FEED SYNC J 4 ED 2 c SYNC {4 FIG. 38.

A I1 ]L A+9o 1 F1 PATENTEU JUL 3 I975 SEEI5N6 FIG. 5 I m o l 2 3 3 ROLR 2 SYNC 2 2 2 2 4/3 FEED SYNC] S R /PAPR SOP 9 iii Z/fl fi/Z ji SgPAPR 8 777 '38 IO y STAGE SHFT REG W JAM 2 NOT PAPR SENS 2 /ff5a" A Z0? 4 3 NOT PAPR SENSI f%a O JAM 3 ROLR SYNC 074 A JAM 4 mx 2 gPAP R Vii %ZZ LGTH CTR 0 I LENGTH l7 0 o 8%,- 22 0 I II 7 30 I 0 l5 LGTH 0 5f LENGTH 34 I I BUF LGTH DECODE /d' H I .M COMPARE ss CUT 1,4

7 l 2 2' 2 2 2 2 3 ROLF e BIT BIN CTR r PATENTEUJUL 3 ma NOT TRANS RUN A T PRINT HI s13 1 PRlNTER/PLOTTER SHEET TRANSPORT WITH WEB CUTTING MEANS BACKGROUND OF THE INVENTION 1. Field of Invention This invention relates to a variable speed printer/- plotter paper transport capable of feeding paper from a continuous roll, cutting said paper into sheets of variable length, providing a settable fixed spacing between said sheets, and transporting said sheets through the paper transport, the entire aforesaid operation being monitored for the occurrence of paper jams.

2. Description of the Prior Art In the graphic arts, there are innumerable types of mechanisms for advancing graphics-receiving sheets. One type successively feeds precut sheets from stacks; this type is used predominately in high volume production printers, both of the preset-type variety and of the image reproducing variety (such as electrostatic image reproducers). However, this type is found to be too limited for composing-printers of the type which are useful for printing originally-generated information, such as output devices for data processing equipment. Such printers frequency use a more convenient arrangement in which paper is fed from a continuous roll and/or fanfold stock, with or without separation into individual sheets. However, such transport mechanisms are unable to provide variably-sized, cut sheets under control of a data processing program. Also, such devices tend to put constraints on the rate of throughput of printing to be achieved by a system in which they are employed.

SUMMARY OF INVENTION The object of the present invention is to provide a versatile paper transport mechanism well suited for utilization in a system for printing or plotting information generated by a data processing system. Other objects, relating to such a paper transport mechanism, include the provision of:

Distinct, multi-sheet jam detection means;

Variable sheet size capability;

Controllable, minimum intersheet spacing capability; and

A variable speed sheet feeding mechanism having features satisfying one or more of the above objects.

According to the present invention, a variable speed web transport mechanism is synchronized with signals relating to the advancement of a web, such as by revolutions of rollers used to advance paper, whereby functions are properly synchronized, regardless of the selected transport speed. In further accord with the present invention, one section of the feed path through a web transport mechanism has web, such as paper removed therefrom more slowly than it is fed thereto so as to form a loop; web fed to the loop is stopped to permit tear-free cutting into sheets. Subsequent startup is variously timed according to settable designations of desired, different sheet lengths and desired constant spacing between sheets. The advancement of a plurality of successive sheets through the transport is monitored by inserting into a correspondingly-advanced shift register an information bit, the advancement of which through the shift register parallels the advancement of the related sheet through the transport. Failure of the sheet to emerge at a time commensurate with the timing of the emergence of the related bit from the shift register is utilized as a paper jam indication. In further accord with the invention, each sheet is logged into and out of the transport to provide an indication of when all sheets are clear of the transport.

The present invention provides for the feeding of paper from a continuous roll, cutting the paper into variable length sheets under control of settable indicia, such as may be provided by the output of a computer program, and inserting fixed spacing of minimum proportions between sheets to ensure maximum throughput of the sheets through the transport mechanism. The technique employed in achieving these features of the invention involves the building up of a paper loop by means of differential speed rollers, and, at a time when a suitably programmed counter indicates that the desired sheet length has been attained, halting the paper feeder mechanism to permit tear-free cutting of the paper. Subsequent to cutting of the sheet, control circuitry causes the feeding of the next sheet to be delayed until the loop buildup has been depleted and the desired intersheet spacing has been inserted, all of which is determined by a presettable up/down counter. The paper feeder mechanism then advances paper up to a point where it is synchronized to another portion of the paper transport mechanism; at this point the control mechanism can either terminate the cutting and feeding of further sheets and permit the previous sheet to pass through the further portion of the transport mechanism, or it may permit continuous cutting and feeding of additional sheets through the mechanism as described hereinbefore. Additionally, apparatus in accordance with the present invention has a capability of monitoring the travel of sheets through the mechanism on a sheet by sheet basis in a manner so as to detect the occurrence of paper jams within the mechanism, independent of sheet size and speed of operation of the apparatus. In the present embodiment, the apparatus also includes means to automatically shut off the paper transport after the last sheet has completely emerged therefrom.

A feature of the invention is that it is independent of conventional fixed timing circuitry since its timing is completely synchronized to the rollers of the system; therefore, synchronization is maintained even though the apparatus is operated at different speeds. Another feature is that since independent jam detection is provided for several sheets in transit therethrough, the apparatus in accordance with the present invention is capable of feeding multiple sheets with minimum intersheet spacing.

Other objects, features and advantages of the present invention will become more apparent in the light of the following detailed description of a preferred embodiment thereof, as illustrated in the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematicized illustration of a paper transport mechanism incorporating a preferred embodiment of the present invention;

FlG. 2 is a timing diagram illustrating timing relationships in the disclosed embodiment of the present invention;

FIG. 3 is a schematic block diagram of synchronizing circuits incorporating in the preferred embodiment of the present invention;

FIG. 3a is a timing diagram of the circuit of FIG. 3;

FIG. 4 is a simplified schematic block diagram of feed and run control circuitry incorporated in the disclosed embodiment of the present invention and of intersheet and transport idle controls in accordance with the present invention;

FIG. 5 is a simplified schematic block diagram of a cut control and paper jam controls in accordance with the present invention, and other circuitry incorporated in the disclosed embodiment thereof; and

FIG. 6 is a simplified schematic diagram of feed and speed controls in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The embodiment is disclosed herein in the same fashion as it is presented in FIGS. 21-25 and FIG. 13 of a copending application of the same assignee, Ser. No. 67,185, now US. Pat. No. 3,634,828, filed on even date herewith (Aug. 26, 1970) by Myers and Sharp and entitled GRAPHICAL DATA PROCESSING SYS- TEM. The figure numbers have been renumbered herein, FIGS. 1 through 5 comprising FIGS. 21 through 25 of said copending application and FIG. 6 herein comprising FIG. 13 of said copending application. The numbers at the borders of the figures indicating sources and destinations of signal lines are enclosed in parenthesis whenever such numbers refer to figure numbers in the aforementioned copending application, and without parenthesis to refer to figure numbers herein.

Referring now to FIG. 1, the printer includes an imaging device 500 which in the present embodiment comprises a cathode ray tube having a fiber optic face plate for improved image resolution. Paper is fed from a continuous roll out to predetermined lengths, and beneath a charger station 502 where the paper receives an electrostatic charge. As the charged paper passes over the CRT imager, each binary ONE in the video unblanks the beam to deplete the charge on the paper at a given spot. The beam sweeps across the paper in a direction (assumed to be into the page as seen in FIG. 1) perpendicular to paper motion as the paper advances (from right to left in FIG. 1) beneath the CRT imager 500. The paper passes a developer which applies toner to the latent charge image, and then passes a fuser which may apply heat or pressure in any number of well known ways to fuse the toner at the chargedepleted spots on the paper. The paper is then lodged in a stacker 508. The printer of FIG. 1 also comprises the paper handling mechanism to cause the advancement of the paper through the apparatus just described. The paper handler comprises two main sections: the first section is the feeder 510 which supplies uncut paper from a continuous paper roll 511, cuts it to desired lengths, and passes the cut sheets to the other section the transport 512. The paper feeder feeds paper slightly faster than the paper transport moves paper, for reasons described hereinafter. In the present embodiment the paper transport 512 may operate either at 1.8 or 3.6 inches per second. Paper motionthrough the feeder and transport sections is governed by corresponding motors 514, 516, each of which has a related motor control circuit 518, 520. The motor 514 drives the feed rollers 522 whereas the motor 516 drives the transport rollers 524. Such systems are well known in the art and will not be described further.

In the present embodiment (as is described with respect to FIG. 12 in said system) for the printer ready signal, paper has to be fed through the rollers 522 to a point in the feed where the edge of the paper is sensed by a paper sense one (papr sensi) apparatus 526. This apparatus may comprise a light and an optical detector of the type well known in the art and commonly used for such purpose. This feeding of the paper may be done by special controls (not shown herein) or manually by releasing the clutches on the rollers 522, all as is known in the art. The paper feeder section 510 also includes a paper cutter 528 which responds to a CUT signal on a line 530 to cause cutting of the paper. In order to have the paper stopped at the time a cut is made, not only does the feeder 510 run at a higher speed than a transport 512 so as to generate a loop 532 but the feed motor 514 is temporarily halted so that the rollers 522 are stationary when a cut is made. In order to detect the amount of paper fed through the rollers 522, they are provided with a ROLLER ONE sensor (ROLR 1) 534 which may comprise a light shining through a diametric hole in the roller or a drive shaft thereof, or suitable other mechanical signalling. In the present embodiment, it is assumed that each roller has a one inch circumference, and that a diametric sensor is utilized so that one pulse is generated by the ROLLER ONE sensor for each half inch of paper fed therethrough. A similar sensor (ROLR 2) 536 is provided in the transport section 512 in order to keep track of the amount of paper fed therethrough. Also, a paper sensor (PAPR SENS 2) 538 at the end of the transport section 512 senses a sheet of paper reaching the end of the transport section 512. An arrow 539 indicates the position of the leading edge of paper at the time that the paper start of page (SOP) signal is gnerated (as described with respect to FIG. 5, hereinafter.) General timing of the feed section is illustrated in FIG. 2.

Referring now to FIG. 3, all of the sensing relating to the paper handler is synchronized to phase two timing signals (from FIG. 3 of said system) on the line 69 by a plurality of synchronous single shots 544547, with the exception of paper sensor 1, which is utilized without synchronization. At the top of FIG. 3, a four bit closed loop ring 550 advances once for each phase two signal as illustrated by the timing chart in FIG. 3A. The first and third stage outputs are utilized as phase A and phase B for synchronizing the single shots 544-547, and the second and fourth stages are used as phaseplusstages to separate Phase A and Phase B by a suitable interval. The single shot 554 is triggered by the negative transition of a paper sensor two signal on a line 538a, as synchronized with the phase B signal on a line 548, and clocked with the phase two signal on a line 69. Thus, each time a sheet clears paper sensor two, it'provides a signal and since the signal shot 544 is clocked which a phase two signal next following the phase B signal which synchronizes it, a paper two synch (PAPR 2 SYNC) signal will appear on a line 550 during one of the times indicated as phase B plus 90 in FIG. 3a. Similarly, the single shot 545 is triggered by the fall of a ROLLER 1 signal on a line 534a, as synchronized with the phase A signal on a line 552 and clocked to the phase two signal on the line 69 so as to generate a roller one synch (ROLR l SYNC) signal on a line 554. The

signal on the line 554 will coincide with one of the signals indicated as phase A plus 90 in FIG. 3a. The single shot 546 is triggered by the negative transition at the end of a ROLLER 2 signal on a line 536a, synchronized with the phase B signal on the line 548, and clocked with the phase two signal on the line 69 so that its output, a ROLR 2 SYNC signal on a line 556, will correspond in time with one of the signals indicated as phase B plus 90 in FIG. 3a. The signal shot 547 is triggered with the rise of a feed signal on a line 274, synchronized with the phase A signal on the line 552, and gated with the phase two signal on the line 69 so that a FEED SYNC signal on the line 560 coincides with one of the signals indicated as phase A plus 90 in FIG. 3a.

In FIG. d, the FEED signal on line 274 is generated by a flip flop 566 which is clocked by the negative transition of an OR circuit 568 in response to a PAPR SENS 1 signal on a line 526a, or in response to an AND circuit 570. The flip flop 566 is enabled so as to assume a set state (thereby to generate the FEED signal) on the line 274 in response to a LOGIC FEED signal on the line 262. As described with respect to FIG. 6, hereinafter, this signal indicates that the control logic is commanding the paper handler to feed a sheet of paper. When the logic feed signal appears on line 262, it will have no immediate effect on the trigger 566, pending an output from the OR circuit 568 to clock the trigger 566. This will be generated by the AND circuit 570 in response to a delay circuit 572 which provides an output after a certain delay from the turn on of a transport run latch 574. This latch is turned on by a single shot 576 in response to the logic feed signal on the line 262. The delay unit 572 has sufficient delay to permit the transport stages to attain their rated speed prior to enabling the AND gate 570.

The offside (NOT Q) of the flip flop 566 is fed to an AND circuit 578 gated with the logical event of paper sensor one (526, FIG. 1) indicating that the edge of the sheet has appeared therebeneath. Thus, with the trigger 566 in the off state, and paper advanced to the point where it provides a signal under paper sensor one (526, FIG. I), the AND circuit 578 will generate the PRNTR RDY signal on the line 216. As described with respect to FIG. 12 in said system this is to enable operation of the go switch to cause a system go reset to generate the first tape go signal to begin reading information into the system from tape. The system go reset also sets the logic feed latch 263, in FIG. 6, so that once print line information is being received and the dynamic run trigger (246, FIG. 12 of said system) is set, AND circuit 260 in FIG. 6 will generate the logic feed signal on line 262 to cause paper feeding to begin. The logic feed signal on line 262 first sets the latch 574 to generate the transport run signal on the line 286 which is utilized in FIG. 1 to actually cause the paper transport motor control 520 to energize the motor 516 thereby causing the rollers 524 of the paper transport section 512 to commence motion. Once these are in motion, each half revolution of the first transport roller 524 will cause the roller two sensor 536 to initiate a signal resulting in a roller two synch signal on the line 556. After a suitable delay as determined by the delay unit 572, the AND circuit 570 will respond to a roller two synch signal on the line 556 to cause the feed trigger 566 to become set. The NOT CUT ENABLE signal on a line 580 will in this sequence enable an AND circuit 582 to generate a FEED RUN signal on the line 584, which signal causes the paper feed motor control 51 8 of FIG. 1 to energize the motor 514 thereby causing the paper feeder section 510 to advance paper from beneath the paper sensor one 526 through the first rollers 524 towards the charger 502. The feed will continue to run until the total length of paper desired for a sheet has been positioned in advance of the cutter 528 (FIG. 1), and a sufficient loop of paper 532 (FIG. I) has been built up due to the speed differential between the transport and feeder sections. Then, in the manner described hereinafter, the cut signal on the line 530 causes a latch 584a to be reset so that it no longer presents the NOT CUT ENABLE signal on the line 580. This removes the FEED RUN signal from the line 584, which in turn halts the feed rollers 522 (FIG. 1) causing the paper under the cutter 528 to be stationary during the cut operation. Note that the transport rollers 524 remain continuously in motion thereby permitting the synchronous printer/plotter operation required by the CRT imager 500. In this condition, that is with the feeder section halted and the transport section in operation, the aforementioned paper loop will be depleted and an inter-sheet spacing will appear between the cut sheet in the transport and the uncut paper in the feeder. As such time as sufficient inter-sheet spacing has been inserted, the latch 5840 is again set (as described hereinafter), permitting the paper feeder section 510 (FIG. 1) to resume feeding paper from the continuous roll until such time as the uncut paper again appears beneath the paper sensor one 526; at that time the OR circuit 568 clocks the trigger 566 at the same time that the paper sense one signal on the line 564 provides a negative signal at the K input to the feed trigger 566; regardless of whether the LOGIC FEED signal is still present, the trigger 566 toggles from a set condition into the reset condition. The feed unit will now wait until it receives another roller two synch signal through the AND circuit 570; as described hereinafter, the transport run latch 574 will remain set until all paper has cleared the paper transport section 512. This function is controlled by an OR circuit 586 which will reset the latch 574; in normal operations (other than start up and jams) the OR circuit 586 is operated by a signal on a line 590, which indicates that the last sheet which has been fed by the paper feeder has in fact passed beneath paper sensor two 538 (FIG. I) and is in the stacker 598. This signal is generated by a borrow out of the highest order stage of a four stage up/down idle counter 592. When the system is first turned on, the PWR ON RST signal on the line 232 presets the counter 592 to all ones, which is equivalent to minus one. Thereafter, each time the feed trigger 566 is turned on, a feed synch signal will appear on line 560 to increment the count in the up/down counter 592. This effectively logs-in the sheets sent by the paper feeder section 510 to the paper transport section 512. Then, for each sensing of a sheet by the paper sensor two 528 (FIG. 1) there will be a PAPR 2 SYNC signal on the line 550 which logs the sheet of paper out of the paper transport unit by causing the up/down counter 592 to count down by one count. FEED SYNC is timed to phase A plus (FIG. 3a) and PAPR 2 SYNC is timed to phase B plus 90, so the up and down counts never interfer with each other. As the last sheet fed is sensed passing under paper sensor two 538, that particular paper two synch signal on line 550 will cause the up/down counter 592 to count to minus one (an all ones condition) and generate a borrow signal out of the highest order, which comprises the signal on the line 590, and operates the OR circuit 586 which resets the transport run latch 574. The OR circuit 586 is also operated by the PWR ON RST signal on the line 232 when the system is turned on, and by ajam reset signal generated on a line 594 as a result of operating a JAM RST switch 596. In addition, an AND cicuit 598 will cause the OR circuit 586 to reset the transport latch 574 in response to a JAM 2 signal on a line 600 concurrently with the absence of the feed signal on the line 274. This is a convention (a matter of design choice) that allows the transport to run until a normal feed stop. A similar OR circuit 599 resets the FEED trigger 566 in response to power on reset, LOGIC FEED, or a JAM 1 signal on a line 601. The nature of the JAM l and JAM 2 signals is described with respect to FIG. 5 hereinafter.

At the top of FIG. 4, another four stage up/down counter 602 serves to maintain a constant sheet-tosheet spacing during repetitive feed operations (when the transport unit is running continuously and the paper feeder is running so as tosupply it with successive sheets). The counter 602 maintains a dynamic count representing the amount of paper within the loop 532 (FIG. 1) by being incremented in response to a ROLR l SYNC signal on the line 554, and decremented by a ROLR 2 SYNC signal on the line 556. The counter is initially preset for each sheet fed by an amount which represents the desired intersheet spacing. In the present embodiment, each of the roller synch pulses represents one half inch of paper fed through the related roller. The paper feeder section 510 operates at a speed which is slightly higher than the speed of the paper transport section 512. Thus, even though paper is being removed by the transport section while paper is being fed by the feeder section, the loop (and the count within the counter) will continue to build up while the desired sheet length is being attained. At such time that said desired sheet length has been attained the feeder can be stopped (because of the loop buildup) so that cutting can occur upon a stationary section of paper while the transport continues to remove paper from the loop 532. Once the sheet is cut, the loop (and the count within the counter) must be allowed to fully deplete and an intersheet spacing inserted prior to allowing the paper feeder 510 to begin feeding the next sheet of paper. The desired intersheet spacing is attained by initially presetting the up/down counter 602 to one less than the binary value of said desired intersheet spacing, where each binary bit represents one half inch (since each of the pulses which increment or decrement the counter represents one half inch of paper fed). Presetting the counter is accomplished under control of a latch 604, which is set by each feed synch signal on the line 560 and reset by a counter borrow signal on a line 606. Resetting of the latch 604 causes forced presets to be applied to the counter 602 while setting of the latch permits normal up/down counting. Assuming as an example that a one inch intersheet space is desired, the counter will have originally been preset to one (with the lowest ordered stage set and the remaining stages in the reset state); after being incremented and decremented for some equal number of ROLR l and ROLR 2 SYNC signals, as occurs in normal operation, the counter will have returned to a one count, the loop will have been fully depleted, and no inter-sheet spacing will exist. The next roller two synch pulse (A inch spacing) will cause the counter to decrement to a count of zero, and the following roller two synch pulse (one inch spacing) will cause it to be set to minus one (an all ones condition) which generates the borrow signal on the line 606. Thus, the counter 602 must be preset to a binary count which is greater than minus one (all ones condition) by one binary count per half inch of desired intersheet spacing. This presetting is controlled by a plurality of switches 608-610, which can be set at the start of any job to provide the desired intersheet spacing. For a one inch intersheet gap, switch 608 is closed causing an OR circuit 612 to preset the lowest ordered stage, as described in the above example. For a one and one half inch intersheet space, closing of a switch 609 causes an OR circuit 614 to preset the counter to a count of two (the second order stage only), which requires one additional half inch to have been sensed by the roller synch two signal before the borrow is generated. Note that the preset condition is forced on the counter 602 by the latch 604 from the time the borrow signal is generated until the following feed synch signal is received; this merely prevents the counter from operating during the period when there is no loop buildup to be monitored.

Referring to FIG. 5, the paper start of page (PAPR SOP) signal on line 418 generates, in FIG. 18 of said system, the first memory buffer ready signal (thereby denoting that printing may begin from one half of memory, and that data for additional print lines may be read into the other half of memory). The paper SOP signal on line 418 is generated by the output of a four bit binary counter 610, which indicates a count of 16 roller two synch signals on the line 556; since in the present embodiment each roller two synch signal is the equivalent to one half inch of paper feed, this indicates that eight inches of paper have advanced into the paper transport section 512 and that the leading edge of the paper has just reached the CRT imager, indicated by the arrow 539 in FIG. 1. Each time that a paper SOP signal is generated on a line 418, it resets a latch 612, the reset side of which forces the counter 610 to remain in an all zeros state without regard to the receipt thereat of roller two synch pulses on the line 556. Thus the counter 610 cannot operate from the time of paper SOP until a following feed command is indicated by a feed synch signal on the line 558 which sets the latch 612. Stated alternatively, the counter 610 will count roller two synch pulses from the initiation of a feed command until the leading edge of the paper has traversed eight inches, at which point it ceases counting, having generated the paper SOP signal on the line 418.

At the bottom of FIG. 5, the CUT signal is generated on the line 530 in response to a single shot 614 which is triggered by the output of a comparison circuit 616. The comparison circuit 616 compares the output of a binary length decode circuit 618 with the count contained in a six bit binary count 620. The length decode circuit 618 utilizes the length designators in the page/- product control character buffer (FIG. 7) of said system to decode the desired length of each sheet of paper, as illustrated in the chart 622 of FIG. 5. Thus if the sheet length is to be 8 A inches, both of the bits (LGTI-l O, LGTI-I 1) will be ZEROS. Eleven inch sheet length is designated by LGTH 0 being a ZERO and LGTl-I 1 being a ONE; 15 inch paper length is designated by LGTH 0 being a ONE and LGTH 1 being a ZERO; when both bits are ONEs, a length of 17 inches is indicated. Since the roller one synch pulses on line 554 indicate one half inch per pulse of paper fed through the paper feeder 510, twice as many pulses must be received as inches of length desired. When the counter 620 advances to a count equal to twice the number of desired inches, the compare circuit 616 provides the output to generate the CUT signal on the line 530.

As a precaution in paper handling, two different paper jam designating signals are generated under certain conditions. The JAM 1 signal on the line 601 detects any failure in feeding paper up to paper sensor one 526 (FIG. 1 In the present embodiment, there are approximately I '76 inches between the cutter 528 and the first paper sensor 526 (FIG. 1); consequently, if paper has not reached the first sensor 526 by the time that sufficient paper has been fed, then the JAM l signal on the line 601 will be generated. To accomplish this, an AND circuit 624 responds to a signal on a line 626 indicating that stage 3 of the cut counter 620 has been set, indicating 2 inches of paper have been fed from the cutter toward the first paper sensor 526 (FIG. 1). If the first paper sensor 526 has not been operated by that time, then a NOT PAPR SENS 1 signal on a line 526a, gated with the roller one synch pulse on line 554, will cause the AND circuit 624 to generate the JAM 1 signal on the line 601.

The JAM 2 signal on the line 600 indicates a failure in timely passage of cut sheets through the transport section 512. When a feed command is generated, paper proceeds through the transport and ultimately passes under the second paper sensor 538 (FIG. I) as it emerges into the paper stacker 508. The desirable precaution is therefore to monitor the passage of the various length paper sheets through the transport and check for their emergence at the stacker. Since the transport section is approximately 4 feet long, up to four or five different sheets of paper may be in transit within the transport unit at any one time. In the present invention, means are provided to create a pulse for each sheet of paper as it enters the transport, andto advance each of these pulses through a shift register so the advancement of the pulse through the'shift register roughly parallels the advancement of the actual sheet through the transport. The emergence of the pulse from the shift register therefore provides an indication that the related sheet of paper should have passed under paper sensor two. At the top of FIG. 5, an AND circuit 630 senses when the start of page counter has reached a count of 13, indicating that approximately 6 92 inches of the sheet have been fed through the roller two sensor 536. This pulse therefore relates to that sheet of paper currently advancing th the CRT imager. The signal from the AND circuit 630 proceeds over a line 632 to the first stage of a 10 stage shift register 634, which is advanced once for each 4 inches of paper fed by a signal on a line 636 from a divide-by-eight circuit 638, which may comprise a simple three stage counter. Thus for each roller two synch signal on the line 556, a signal indicating four inches of paper feed appears on the line 636. The ten stage shift register is of the type readily available on the market, and responds to the fall of the signal on the line 636 so that when a four inch pulse is available thereon, and any of the pulses introduced into the 10 stage shift register have advanced to the last stage thereof, there must be paper beneath paper sensor two; otherwise a NOT PAPER SENSE 2 signal on the line 538a will gate the AND circuit 640 and generate a JAM 2 signal on the line 600. Notice that the criticality of the timing adjustment is merely that, for the various sizes of paper sheets which can pass through the transport, the ten stage shift register 634 should not have an output coincident with a 4 inch pulse 636 at a time when a valid intersheet space may be passing underneath paper sensor two.

At the top of FIG. 6, an AND circuit 260 generates the LOGIC FEED signal on the line 262 which causes the feed flip flop in the paper handler section (as described with respect to FIG. 4 hereinbefore) to become set and thus allow the feeding of one sheet of paper. The AND circuit 260 is enabled by the presence of the DYN RUN signal on line 245 (in said system) concurrently with the output of the latch 263 provided no speed change requirement exists as indicated by an inverter 264, as described hereinafter. The latch 263 is initialy set at the time that the operator presses the GO switch 224 (FIG. 12 of said system) as a result of a SYS GO RST signal on the line 97 (in said system) enabling an OR circuit 268. The OR circuit 268 can also respond to an AND circuit 270 when in the product mode (253) and prior to the end of printing, as indicated by a NOT INTRPT FEED signal on a line 272, so as to hold a continuous set on the latch 263. This results in a constant LOGIC FEED signal on line 262 which is interpreted by the paper feed control section, as described hereinafter, as a command to feed multiple sheets. Multiple sheets will normally be fed until an interrupt feed signal (indicating an approaching end of product) is received, or an operator switches the system from PRODUCT to PAGE mode. Had the system been in the PAGE mode at the outset, the FEED signal on line 274 which results from the logic feed signal on line 262 would have reset the latch 263 (in the absence of the continuous set described hereinbefore) and only a single sheet of paper would have been fed.

The inverter 264, which prevents the AND circuit 260 from operating whenever a speed change is pending, responds to an exclusive OR circuit 278 which compares a control character indication of whether high speed operation is to be utilized or not, as manifested by a HI SPD signal on a line (from said system) with the setting of a trigger or flip flop 280, the affirmative output of which comprises a PRINT HI SPD signal on a line 282 which controls the rate of paper handling as described with respect to FIG. I hereinbefore. The flip flop 280 can be triggered by the output of an AND circuit 284. Each time the AND circuit 284 operates, the flip flop 280 will alter its state. The AND circuit 284 will operate in responseto an output from the exclusive OR circuit 278, which is an indication that the speed called for by the program (line 80) is different than the speed commanded by the trigger 280 (line 282). However, the circuitry is interlocked in such a fashion that the speed cannot be changed whenever the transport is running, as controlled by a NOT TRANS RUN signal on a line 286 (described with respect to FIG. 4 hereinbefore) nor can it operate when the LOGIC FEED signal is present on line 262, due to an inverter 288. In summary, whenever the paper transport is not running or being commanded to run, flip flop 280 may be altered to bring it into agreement with the speed command on line 80.

The inputs to the circuitry of FIG. 6 from said system comprise simply commands to feed paper and commands indicating that paper feeding should stop.

Although the invention has been shown and described with respect to a preferred embodiment thereof, it should be understood by those skilled in the art that various changes and omissions in the form and detail thereof may be made therein without departing from the spirit and the scope of the invention.

Having thus described a typical embodiment of our invention, that which we claim as new and desire to secure by Letters Patent of the United States is:

l. A web transport apparatus adapted for handing an image receiving web, comprising:

feed means for advancing a continuous length of the image receiving web through a first station at a first speed;

transport means for receiving the web from said feed means and for continuously feeding the web at a speed less than said first speed past a plurality of additional stations operative upon a sheet to be cut from said web to create an image thereon;

means for generating a signal representation of the actual length of the web fed past said first station;

means presenting a signal representation of a desired sheet length;

means for comparing said actual length signal with said desired length signal and for generating a cut command signal in response to a given relationship therebetween;

means responsive to said out command signal for halting the operation of said feed means;

a paper cutter disposed between said first station and said transport means, said cutter responsive to said out command signal to cut a sheet of such desired length from the web;

tailgate means for generating a signal representation of the length of the sheet between said first station and said transport means; and

means responsive to said tailgate means for causing resumption of operation of said feed means in response to a signal representation indicative of a desired length of sheet and an intersheet gap remaining between said first station and said transport means.

2. A web transport apparatus, comprising:

feed means having first rollers operating at a first speed for advancing a continuous length of image receiving web along a path;

transport means having a plurality of second rollers for receiving the web from said feed means and for continuously feeding the web past a plurality of stations operative upon a sheet to be cut from the web to create an image thereon, said second rollers operating at a speed less than said first speed.

means sensing the revolutions of said first rollers;

means responsive to said first roller revolution sensing means for generating a count signal representation of the actual length of the web fed therethrough;

means presenting a signal representation of a desired sheet length;

means for comparing said actual length signal with said desired sheet length signal to generate a cut command signal when the actual length equals the desired sheet length;

means responsive to said cut command signal for halting the operation of said feed means;

a paper cutter disposed between said first and second rollers, said cutter responsive to said cut command signal to cut a sheet of such desired length from the web;

means sensing the revolutions of said second rollers;

differential count means concurrently responsive to said first and second roller sensing means to maintain a count proportional to the length of the sheet remaining between said first and second rollers; and

means responsive to said differential count means to cause resumption of operation of said feed means in response to an output thereof indicative of a desired length of sheet and an intersheet gap remaining between said rollers.

3. A web transport apparatus according to claim 2 wherein said differential count means comprises:

an up/down counter, the count of said counter being incremented by said first roller sensing means and decremented by said second roller sensing means, whereby the count thereof is indicative of the length of sheet remaining between said rollers, said differential count means further comprising:

means for selectively presetting the count in said counter whereby the count thereof comprises an indication of the sum of the length of sheet between said roller and a desired intersheet spacing represented by the amount by which said count is advanced by said selective presetting. 

1. A web transport apparatus adapted for handing an image receiving web, comprising: feed means for advancing a continuous length of the image receiving web through a first station at a first speed; transport means for receiving the web from said feed means and for continuously feeding the web at a speed less than said first speed past a plurality of additional stations operative upon a sheet to be cut from said web to create an image thereon; means for generating a signal representation of the actual length of the web fed past said first station; means presenting a signal representation of a desired sheet length; means for comparing said actual length signal with said desired length signal and for generating a cut command signal in response to a given relationship therebetween; means responsive to said cut command signal for halting the operation of said feed means; a paper cutter disposed between said first station and said transport means, said cutter responsive to said cut command signal to cut a sheet of such desired length from the web; tailgate means for generating a signal representation of the length of the sheet between said first station and said transport means; and means responsive to said tailgate means for causing resumption of operation of said feed means in response to a signal representation indicative of a desired length of sheet and an intersheet gap remaining between said first station and said transport means.
 2. A web transport apparatus, comprising: feed means having first rollers operating at a first speed for advancing a continuous length of image receiving web along a path; transport means having a plurality of second rollers for receiving the web from said feed means and for continuously feeding the web past a plurality of stations operative upon a sheet to be cut from the web to create an image thereon, said second rollers operating at a speed less than said first speed; means sensing the revolutions of said first rollers; means responsive to said first roller revolution sensing means for generating a count signal representation of the actual length of the web fed therethrough; means presenting a signal representation of a desired sheet length; means for comparing said actual length signal with said desired sheet length signal to generate a cut command signal when the actual length equals the desired sheet length; means responsive to said cut command signal for halting the operation of said feed means; a paper cutter disposed between said first and second rollers, said cutter responsive to said cut command signal to cut a sheet of such desired length from the web; means sensing the revolutions of said second rollers; differential count means concurrently responsive to said first and second roller sensing means to maintain a count proportional to the length of the sheet remaining between said first and second rollers; and means responsive to said differential count means to cause resumption of operation of said feed means in response to an output thereof indicative of a desired length of sheet and an intersheet gap remaining between said rollers.
 3. A web transport apparatus according to claim 2 wherein said differential count means comprises: an up/down counter, the count of said counter being incremented by said first roller sensing means and decremented by said second roller sensing means, whereby the count thereof is indicative of the length of sheet remaining between said rollers, said differential count means further comprising: means for selectively presetting the count in said counter whereby the count thereof comprises an indication of the sum of the length of sheet between said roller and a desired intersheet spacing represented by the amount by which said count is advanced by said selective presetting. 